The Hergiswil water supply company is an ISO 9001-certified and reliable supplier of drinking water for its customers.
Due to measurement failures at low flow rates at the reservoir outlet (<70 l/min), which are attributable to the principle-based operation of EMFs, WV Hergiswil was looking for an alternative measurement method that could also precisely record the smallest flow rates at night. Replacing the existing EMF measuring point (magnetic-inductive flow measurement) with a clamp-on system proved to be the right decision. The chosen solution is cost-effective, but of high technical quality.
Reference measurement as a basis for decision-making
The reference measurements carried out in the Unterstalden reservoir showed beyond doubt that the clamp-on system is much more reliable and can also record lower flow velocities than the MID system. (See illustrations) This property was utilised to remove the existing pipe taper to DN200 so that a DN300 system is now available throughout.
Illustration: It is clearly recognisable that the clamp-on measurement, in contrast to the MID measurement, also records the low flow rates during the night
Drift-free flow measurement
The measuring instruments do not require any zero-point calibration during installation and have a permanently drift-free measurement. This feature is a unique selling point on the market. Another advantage is the ultrasonic transit time difference measurement method, which enables precise measurement from a flow velocity of 2.5 mm/s. In contrast to MIDs (magnetic inductive flow measurement, from 150 mm/s), it can therefore also be used at very low flow velocities. In order to detect leaks, changing water draws and for billing purposes, a measuring technology that can also detect the smallest quantities in addition to the usual large draws is indispensable. The design of the sensor system outside the pipe ensures effective protection against lightning strikes, which is a decisive advantage.
Simple installation
Furthermore, the installation costs are significantly lower than with other systems, as no intervention in the pipework is required. With the new clamp-on measuring point, the Hergiswil water supply has increased the reliability and precision of its measurement data.
